Humidifier

ABSTRACT

A humidifier including an inner case of the shape of a cylinder having a bottom, an outer case of cylindrical shape arranged to be concentric with the inner case, and a plurality of hollow fiber membranes being placed in the space between the two cases and formed into a hollow fiber membrane bundle of a cylindrical shape, wherein fluid pathways are provided which connect from the interior part to the exterior part of the hollow fiber membrane bundle. The humidifier allows all of the hollow fiber membranes to take part in humidification effectively, and thus exhibits improved efficiency in humidification.

This is a nationalization of PCT/JP01/09702, filed Nov. 6, 2001 andpublished in Japanese.

TECHNICAL FIELD

This invention relates to a humidifier for humidifying gas supplied toe.g., a fuel cell.

BACKGROUND ART

In a polymer electrolyte fuel cell, a device for humidifying andsupplying a fuel gas such as hydrogen, etc., and an oxidizer gas such asoxygen, etc. (hereinafter both are called a reaction gas) is required.

For example, a device utilizing a hollow fiber membrane as disclosed inJP-A-8-273687 is known as such a humidifier.

The humidifier in the conventional art will be explained by reference toFIG. 5. FIG. 5 is a schematically sectional view of the humidifier inthe conventional art.

As shown in this figure, the humidifier 100 in the conventional artconsists schematically of a case 101 and a hollow fiber membrane bundle102 filled within this case 101.

The case 101 is approximately formed in a cylindrical shape, and has anopening portion 101 a at one end of the cylinder and an opening portion101 b at the other end. Further, the case 101 has opening portions 101c, 101 d on its sidewall.

And, the hollow fiber membrane bundle 102 is filled within this case101. One end of the hollow fiber membrane bundle 102 is sealed betweenthe outer wall faces of the hollow fiber membranes and between the outerwall faces of the hollow fiber membranes and the inner wall face of thecase 101 so as to open only the hollow interior in the opening portion101 a. The other end of the hollow fiber membrane bundle 102 issimilarly sealed between the outer wall faces of the hollow fibermembranes and between the outer wall faces of the hollow fiber membranesand the inner wall face of the case 101 so as to open only the hollowinterior in the opening portion 101 b.

Also, a clearance 103 is arranged on the side face side of the hollowfiber membrane bundle 102 between the hollow fiber membrane bundle 102and the case 101.

Thus, a first path entering the hollow interior of the hollow fibermembrane of the hollow fiber membrane bundle 102 from the openingportion 101 a side (arrow S0), and reaching the other end side of thehollow fiber membrane bundle 102 through the hollow interior (arrow S1)is arranged. Further, a second path entering the interior of the case101 from the opening portion 101d (arrow T0), and reaching the exteriorof the case 101 from the opening portion 101 c through the clearance 103is arranged.

Thus, for example, the reaction gas is flowed to the first path andwater is flowed to the second path so that the reaction gas within thefirst path is humidified by transmitting the water within the secondpath through the membrane of the hollow fiber membrane and diffusingthis water into the first path.

Since the humidifier is constructed so as to perform a humidifyingaction by utilizing that water is transmitted through the membrane ofthe hollow fiber membrane in this way, the humidifying action isaccelerated as the area of the flowing water coming in contact with thehollow fiber membrane is increased.

However, in the above conventional art, since the construction forsetting plural hollow fiber membranes to a columnar bundle and flowingwater onto its outer circumferential wall face is used, the water isflowed onto the outer circumferential surface of the bundle along theaxial line. Thus, there are defects in that no water is sufficientlypermeated to the interior of the bundle, and no hollow fiber membranenear the center of the bundle effectively functions, and humidifyingefficiency is low.

An object of the present invention is to provide a humidifier forimproving the humidifying efficiency.

DISCLOSURE INVENTION

To achieve the above object, the present invention resides in ahumidifier characterized in that the humidifier comprises:

a sleeve-shaped inner case having a bottom;

a sleeve-shaped outer case concentrically arranged with respect to theinner case; and

a hollow fiber membrane bundle filled in an annular clearance betweenthe outer case and the inner case;

wherein the humidifier further comprises:

a first path from one end side of said hollow fiber membrane bundle tothe other end side through the hollow interior of each hollow fibermembrane; and

a second path from a first opening portion arranged on the sidewall ofsaid inner case to a second opening portion arranged on the sidewall ofsaid outer case through between the outer wall faces of the respectivehollow fiber membranes within the hollow fiber membrane bundle; and

a humidifying object gas is flowed to one of said first and secondpaths, and a fluid including moisture is flowed to the other.

Here, the upstream side of the first path may be set to one end side ofthe hollow fiber membrane bundle, and may be also set to the other endside. Further, the upstream side of the second path may be set to thefirst opening portion arranged on the sidewall of the inner case, andmay be also set to the second opening portion arranged on the sidewallof the outer case.

Accordingly, since the second path is arranged so as to reach the outerwall side from the inner wall side of the annular clearance, this pathis extended from the inside diameter side of the hollow fiber membranebundle filled in the annular clearance to the outside diameter side.

It is preferable that said first opening portion is arranged near oneend of the hollow fiber membrane bundle, and said second opening portionis arranged near the other end of the hollow fiber membrane bundle.

Thus, the second path is extended from one end side of the hollow fibermembrane bundle to the other end side.

It is also preferable that a plurality of said first opening portionsare arranged in different positions with respect to the axial direction,and the opening diameters of these opening portions are set to graduallyreduce toward the bottom of the inner case.

Thus, when the fluid is flowed toward the bottom within the sleeve ofthe inner case, the fluid can be flowed from each opening portion intothe hollow fiber membrane bundle with good balance.

It is also preferable that a clearance is formed between the outercircumferential face of said inner case and the inner circumferentialface of said hollow fiber membrane bundle.

Thus, when the fluid is flowed from the first opening portion arrangedin the inner case to the hollow fiber membrane bundle, the fluid can beequally flowed onto the inner circumferential face of the hollow fibermembrane bundle.

It is also preferable that the gas after the humidification is suppliedto a fuel cell.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematically sectional view of a humidifier in accordancewith a first embodiment of the present invention.

FIG. 2 is a perspective view showing an end portion of a hollow fibermembrane.

FIG. 3 is a schematically sectional view of a humidifier in accordancewith a fifth example of the present invention.

FIG. 4 is a schematically sectional view of a humidifier in accordancewith a sixth example of the present invention.

FIG. 5 is a schematically sectional view of a humidifier in theconventional art.

BEST MODE FOR CARRYING OUT THE INVENTION

The preferred embodiments of this invention will next be explainedexemplarily in detail by reference to the drawings. The sizes,materials, shapes, their relative arrangements, etc. of constructionalparts described in these embodiments are not intended to limit the scopeof this invention only to them unless they are particularly specificallydescribed.

A humidifier in accordance with a first embodiment of the presentinvention will be explained by reference to FIGS. 1 and 2. FIG. 1 is aschematically sectional view of the humidifier in accordance with thefirst embodiment of the present invention. FIG. 2 is a perspective viewshowing an end portion of a hollow fiber membrane.

The humidifier 1 in accordance with this embodiment is a device forhumidifying a reaction gas (a fuel gas of hydrogen, etc., and anoxidizer gas of oxygen, etc. as mentioned above) of e.g., a polymerelectrolyte fuel cell.

And, as shown in these figures, the humidifier 1 is schematicallyconstructed by an inner case 3, an outer case 4 concentrically arrangedwith respect to this inner case 3, and a hollow fiber membrane bundle 2filled in an annular clearance between these cases.

The inner case 3 is constructed by a sleeve-shaped member having abottom, and has an opening portion 32 at one end, and also has anopening portion (first opening portion) 31 on the sidewall. A singleopening portion 31 may be arranged and plural opening portions 31(plural with respect to the circumferential direction or the axialdirection) may be also arranged, and they may be provided in accordancewith necessity. Humidifying efficiency can be normally raised as pluralopening portions are provided.

The outer case 4 is constructed by a sleeve-shaped member, and hasopening portions 43, 44 at each end. In the illustrated example, theopening portion 44 is formed on the sidewall so as to perpendicularlybend a path on one end side. An opening portion (second opening portion)41 is also arranged.

The opening portion 41 is arranged on one portion of the circumferenceof a portion of the outer case 4 diametrically increased so as toprovide a clearance 42 between the side face of the hollow fibermembrane bundle 2 and the outer case 4. This is an arrangement toprevent the flow of a fluid flowing through a second path from beingconcentrated onto the vicinity of the opening portion 41 by detouringthe clearance 42.

And, plural hollow fiber membranes 21 are filled in the annularclearance between the inner case 3 and the outer case 4, and form thehollow fiber membrane bundle 2. This hollow fiber membrane bundle 2forms a hollow cylindrical structural body.

Here, each hollow fiber membrane 21 is constructed such that only thehollow interior faces the opening portions 43, 44 at both the ends ofthe outer case 4 and is opened. Namely, in an end portion on the openingportion 43 side, the portion between the outer wall faces of therespective hollow fiber membranes 21, and the portion between theseouter wall faces and the inner wall face of the outer case 4 are sealedby a sealant. Further, in an end portion on the opening portion 44 side,the portion between the outer wall faces of the respective hollow fibermembranes 21, the portion between these outer wall faces and the innerwall face of the outer case 4, and the portion between these outer wallfaces and the outer wall face of the inner case 3 are sealed by thesealant. Thus, only the hollow interior faces the opening portions andis opened at both the ends of each hollow fiber membrane 21.

The opening portion 31 arranged in the above inner case 3, and theopening portion 41 arranged in the outer case 4 are constructed so as tobe located on inner positions (inner in the axial direction) thanpositions sealed by the sealant.

Thus, a first path entering the hollow interior 21 a of the hollow fibermembrane 21 from one end side (opening portion 43 side) of the hollowfiber membrane bundle 2 (arrow S0), and reaching the other end side(opening portion 44 side) of the hollow fiber membrane bundle 2 throughthe hollow interior 21 a (arrow S1) is arranged.

Further, a second path entering the inner case 3 from the openingportion 32 (arrow T0), and entering the clearance between the inner case3 and the outer case 4 from the opening portion 31, and entering theinterior of the hollow fiber membrane bundle 2, and reaching the deviceexterior from the opening portion 41 arranged in the outer case 4through between the outer wall faces of the hollow fiber membranes 21(arrow T1) is arranged.

Routes shown by the arrows of these first and second paths are set toexplain the paths, and do not necessarily mean that the fluid (ahumidifying object gas and a fluid including moisture) is flowed in thedirections shown by these arrows.

In accordance with such a construction, the reaction gas as ahumidifying object gas is flowed to one of the first and second paths,and the fluid including moisture is flowed to the other. Here, water, awet gas (an exhaust gas from cells of a fuel cell can be used), etc. areincluded in the fluid including moisture.

Thus, when the fluid including moisture flows along the membrane wallface of the hollow fiber membrane, the fluid is moved to a flowingpassage of the reaction gas, and the moisture is dispersed into thereaction gas, and the gas is humidified.

This is because, when the gases of different humidities (or moistures)are flowed to the interior and the exterior of the membrane, themoisture flows from the direction of a high water vapor partial pressureto the direction of a low water vapor partial direction in nature, andonly the moisture is transmitted through the membrane in nature.

As mentioned above, in this embodiment, the second path is formed so asto extend through the outer wall face side of the hollow fiber membranebundle 2 forming the hollow cylindrical structural body from the innerwall face of the hollow fiber membrane bundle 2. Therefore, itcontributes to the humidifying action from the hollow fiber membranelocated on the internal side of the hollow fiber membrane bundle 2 tothe hollow fiber membrane located on the external side so thathumidifying efficiency can be improved.

Further, as particularly shown in FIG. 1, the distance of the secondpath with respect to the axial direction can be sufficiently secured byarranging the opening portion 31 on one end side of the hollow fibermembrane bundle 2, and arranging the opening portion 41 on the other endside of the hollow fiber membrane bundle 2 so that the humidifyingefficiency can be further improved.

As mentioned above, the humidifying efficiency can be improved by theembodiment of the present invention. Further, it is thus possible tomake the device compact in equivalent performance, or reduce the numberof used hollow fiber membranes in comparison with the conventional art.

For example, when the hollow fiber membrane bundle is set to have acolumnar structure as in the conventional art and the columnar structureis set to 31 mm in outside diameter and 150 mm in length, 1000 hollowfiber membranes are required. In contrast to this, when the hollow fibermembrane bundle is set to have a cylindrical structure as in thisembodiment and the cylindrical structure is set to 16 mm in insidediameter, 32 mm in outside diameter and 150 mm in length, it issufficient to arrange 750 hollow fiber membranes, and humidifyingperformance can be improved by about 10%.

Here, the humidifying performance is evaluated by a water vaportransmitting amount on a drying gas side when the humidifier is operatedat the pressure and the flow rate of water or a wet gas, and thepressure and the flow rate of the drying gas to be humidified.

The cylindrical structure is set to 13 mm in inside diameter, 26 mm inoutside diameter and 150 mm in length and 550 hollow fiber membranes areused to satisfy the humidifying performance equivalent to that in thecase of the conventional art. Therefore, the device could be madecompact by about 33%.

Some more concrete embodiments will next be explained on the basis ofthe above embodiments.

FIRST EXAMPLE

A polymer material such as polyimide, etc. is used as a raw material ofthe hollow fiber membrane 21. And, the hollow fiber membrane 21 has 3 mmor less (preferably 0.2 to 1 mm) in outside diameter, and plural verysmall holes of several nm are formed on its wall face.

For example, 100 to 10000 hollow fiber membranes 21 are bundled andfilled in the annular clearance between the inner case 3 and the outercase 4 so that the hollow fiber membrane bundle 2 is formed. Asmentioned above, this hollow fiber membrane bundle 2 is formed in ahollow cylindrical shape, and is designed such that its outside diameteris about 1.2 to 3 times the inside diameter and is larger by about 2 to100 mm than the inside diameter (e.g., the inside diameter is set to 10to 100 mm, and the outside diameter is set to 12 to 200 mm). The hollowfiber membrane bundle 2 is also set to about 50 to 500 mm in length.

Further, the portion between the outer wall faces of the respectivehollow fiber membranes 21, the portion between these outer wall facesand the inner wall face of the outer case 4 and the portion betweenthese outer walls and the outer wall face of the inner case 3 are sealedat both the ends of the hollow fiber membrane bundle 2. Furthermore, anadhesive of epoxy resin, urethane, etc. is used as a sealant for fixingthe hollow fiber membrane bundle 2.

A core pipe manufactured by using hard resin such as PC (polycarbonate),PPO (polyphenylene oxide), etc. is used as the inner case 3.

The number of opening portions 31 arranged in this inner case 3 and theposition of the opening portion 31 may be suitably designed inaccordance with the required humidifying efficiency, etc. as mentionedabove. In this example, plural opening portions 31 are arranged at anequal interval near one end side of the hollow fiber membrane bundle 2with respect to the circumferential direction. In contrast to this, theopening portion 41 is arranged in one place in the outer case 4 near theother end side of the hollow fiber membrane bundle 2.

In accordance with such a construction, as shown in FIG. 1, the reactiongas was flowed to the first path from the arrow S0 to the arrow S1, andwater was flowed to the second path from the arrow T0 to the arrow T1.

Thus, the water flowed into the second path flows from the openingportions 31 arranged at the equal interval near one end side of thehollow fiber membrane bundle 2 with respect to the circumferentialdirection to the opening portion 41 arranged near the other end side ofthe hollow fiber membrane bundle 2. Therefore, this water flows by asufficient distance in the axial direction from the interior of thehollow fiber membrane bundle 2 to the exterior.

Accordingly, each of all the filled hollow fiber membranes 21effectively functions. Since the clearance 42 is formed, the waterexuded to this clearance 42 can be easily discharged from the openingportion 41 by detouring the clearance 42. Therefore, no flow isconcentrated onto the vicinity of the opening portion 41.

The humidifier excellent in humidifying efficiency could be realized asmentioned above.

SECOND EXAMPLE

In this example, water flowed to the second path is flowed in thedirection reverse to that in the case of the first example, i.e., fromthe opening portion 41 side to the opening portion 32 side via theopening portion 31 by using the humidifier of the same structure as theabove first example.

In this case, the humidifier excellent in humidifying efficiency couldbe similarly realized.

THIRD EXAMPLE

In the above first example, water is shown as the fluid includingmoisture as a humidifying medium, but a wet gas is used in this example.

Here, since an exhaust gas after generating electricity by fuel cellsholds high humidity in a polymer electrolyte fuel cell, this exhaust gascan be utilized as the humidifying medium (wet gas).

In this case, the humidifier excellent in humidifying efficiency couldbe similarly realized.

FOURTH EXAMPLE

In the above first example, the reaction gas is flowed to the firstpath, and water is flowed to the second path. However, in this example,water or a wet gas is flowed to the first path, and the reaction gas isflowed to the second path. No flowing direction of each fluid islimited.

In this case, the humidifier excellent humidifying efficiency could besimilarly realized.

FIFTH EXAMPLE

A humidifier in accordance with a fifth example of the present inventionwill be explained by reference to FIG. 3.

In the above first example, the opening portion 31 is arranged only nearone end side of the hollow fiber membrane bundle 2. However, thisexample will be explained when plural opening portions 31 are arrangedin different places in the axial direction.

The other constructions and actions are the same as the firstembodiment. Accordingly, the same constructional portions are designatedby the same reference numerals, and their explanations are omitted.

FIG. 3 is a schematically sectional view of the humidifier in accordancewith the fifth example of the present invention.

As shown in this figure, in the humidifier 1 a in accordance with thisexample, plural opening portions are further arranged in differentpositions in the axial direction as the opening portions arranged in theinner case 3 in addition to the opening portion 31 arranged near one endside of the hollow fiber membrane bundle 2. In the illustrated example,opening portions 32, 33 are further arranged in two places.

And, the opening diameters of these opening portions are set so as togradually reduce toward the bottom of the sleeve-shaped inner case 3having the bottom.

In accordance with such a construction, when water or the wet gas isflowed to the second path from the arrow T0 to the arrow T1, theflowing-in amount in the flowing-in of the water or the wet gas fromeach opening portion into the hollow fiber membrane bundle 2 can beadjusted by each opening portion.

Here, when the arranging case of plural opening portions in differentpositions in the axial direction is considered, flow path resistancewithin the hollow fiber membrane bundle 2 is reduced as the openingportion is near T1. Accordingly, if plural opening portions of the samesize are bored, the flow is concentrated onto the opening portion nearT1 so that only one portion of the hollow fiber membrane bundle 2 iseffectively utilized.

Therefore, by reducing the opening diameter of the opening portion nearthe bottom portion, the flow path resistance of this opening portion isincreased and the flow rate of this opening portion is limited. Thus,the water or the wet gas is flowed into the hollow fiber membrane bundle2 with good balance from the opening portion far from T1 so that theentire hollow fiber membrane bundle 2 can be effectively utilized in thehumidification.

Thus, humidifying performance can be set to be best by graduallyreducing and balancing the opening diameter of the opening portion.

Accordingly, each hollow fiber membrane 21 can be more effectivelypractically used, and humidifying efficiency can be raised.

SIXTH EXAMPLE

A humidifier in accordance with a sixth example of the present inventionwill be explained by reference to FIG. 4.

In this example, the arranging case of a clearance 34 between the outercircumferential face of the inner case 3 and the inner circumferentialface of the sleeve-shaped hollow fiber membrane bundle 2 will beexplained.

The other constructions and actions are the same as the firstembodiment. Therefore, the same constructional portions are designatedby the same reference numerals, and their explanations are omitted.

FIG. 4 is a schematically sectional view of the humidifier in accordancewith the sixth example of the present invention.

As shown in this figure, in the humidifier 1 b in accordance with thisexample, the clearance 34 is arranged between the outer circumferentialface of the inner case 3 and the inner circumferential face of thesleeve-shaped hollow fiber membrane bundle 2. Accordingly, when water ora wet gas is flowed to the second path from the arrow T0 to the arrowT1, the water or the wet gas flowed out of the opening portion 31 isflowed to the clearance 34. Therefore, the water or the wet gas can beequally sent to the inner circumferential face of the hollow fibermembrane bundle 2.

Accordingly, each hollow fiber membrane 21 can be more effectivelypractically used so that humidifying efficiency can be raised.

INDUSTRIAL APPLICATION

As explained above, in the present invention, the second path isextended from the inside diameter side of the hollow fiber membranebundle filled in the annular clearance to the outside diameter side.Accordingly, the hollow fiber membranes from the interior of the bundleto the exterior can be practically used so that humidifying efficiencycan be improved.

If the first opening portion is arranged near one end of the hollowfiber membrane bundle and the second opening portion is arranged nearthe other end of the hollow fiber membrane bundle, the second path isextended from one end side of the hollow fiber membrane bundle to theother end side so that the hollow fiber membrane can be more effectivelypractically used.

If plural first opening portions are arranged in different positionswith respect to the axial direction and the opening diameters of theseopening portions are set to be gradually reduced toward the bottom ofthe inner case, the fluid can be flowed from each opening portion intothe hollow fiber membrane bundle with good balance in the flowing caseof the fluid toward the bottom within the sleeve of the inner case sothat the hollow fiber membrane can be more effectively practically used.

1. A humidifier for supplying gas after humidification to a fuel cell,said humidifier comprising: a sleeve-shaped inner case having a bottom;a sleeve-shaped outer case concentrically arranged with respect to theinner case; and a hollow fiber membrane bundle filled in an annularclearance between the outer case and the inner case; wherein thehumidifier further comprises: a first path from one end side of saidhollow fiber membrane bundle to the other end side through a hollowinterior of each hollow fiber membrane; and a second path from aninterior of said inner case to a second opening portion arranged on asidewall of said outer case through a plurality of first openingportions arranged on a sidewall of said inner case and between outerwall faces of the respective hollow fiber membranes within the hollowfiber membrane bundle; said first opening portions being arranged indifferent positions with respect to an axial direction, and the openingdiameters of the opening portions being set to be gradually reducedtoward a bottom of the inner case; and a humidifying object gas flowingto one of said first and second paths, and a fluid including moistureflowing to the other.
 2. A humidifier for supplying gas afterhumidification to a fuel cell, said humidifier comprising: asleeve-shaped inner case having a bottom; a sleeve-shaped outer caseconcentrically arranged with respect to the inner case; and a hollowfiber membrane bundle filled in an annular clearance between the outercase and the inner case; wherein the humidifier further comprises: afirst path from one end side of said hollow fiber membrane bundle to theother end side through a hollow interior of each hollow fiber membrane;and a second path from a first opening portion arranged on a sidewall ofsaid inner case to a second opening portion arranged on a sidewall ofsaid outer case through between outer wall faces of the respectivehollow fiber membranes within the hollow fiber membrane bundle; ahumidifying object gas flowing to one of said first and second paths,and a fluid including moisture flowing to the other; and a clearanceformed between a bottom face of a groove formed on an outercircumferential face of said inner case and an inner circumferentialface of said hollow fiber membrane bundle.